Debates about quantum computing and its impact on crypto are ongoing. While some believe that Bitcoin will die out in the near future others feel it's just scifi. While both sides are missing the point that no quantum computer exists that will be able to break cryptocurrency. Depending on whom you ask, estimates vary tremendously. Optimistic estimates are projected out as far as 2028 through 2030; more cautious estimates are around the end of 2030 through later. However, the specific threats from quantum computers are clear and people/groups are beginning to prepare for it.
As of February 2026, no quantum computer currently exists that can seriously threaten any of the major blockchain networks in the next few years or cause serious damage. The most current reports show a common over-exaggeration of the threat of quantum computers to date; however, the threat of the long-term availability of certain cryptographic algorithms will be done or will no longer use them.
Q-Day is when a fault-tolerant quantum computer can execute Shor’s algorithm and compromise the commonly used public-key encryption technology. Q-Day is described as a time horizon rather than a specific date. While US agencies and experts have often stated that they expect Q-Day to occur sometime around 2035 in order to be prepared, this is not meant to indicate an exact prediction.
Reliable intelligence regarding a quantum computing breakthrough coming in this decade has not been established. Current estimates show that the probability of one occurring before 2030 is extremely low (19%-40% depending on the model), while there is a greater chance of achieving such a breakthrough between 2035 and 2040. Future focus will be placed on mitigating risk through known effects rather than through unrealistic speculation.
Source: Author
Shor's algorithm is disrupting many industries by breaking RSA and Elliptic Curve Cryptography (ECC) based signature systems through the factorization of integers and calculating discrete logarithms. This allows a malicious actor to derive private keys based on public keys, forging signatures on transactions. As such an attack can potentially occur, digital signatures become much less secure.
Grover's algorithm offers a quadratic speedup for brute force search algorithms reducing the effective security of symmetric cryptography and hash functions, such as reducing SHA-256's key length from 256 bits to 128 bits for brute-force search with only one hash value.
While Grover's algorithm does weaken SHA-256 hashes used by Bitcoin and requires adjustment (doubling the size of the key to maintain effective security), it does not completely break them.
Overall, while Grover's algorithm has an overall lesser impact than Shor's does in terms of digital signature systems (with Shor's algorithm posing an existential risk to digital signature systems), the former has a slower execution time and a narrower attack vector for symmetric key systems.
Source: Author
Risks will not arrive all at once:
1) The greatest immediate concern relates to the exposure of one’s public key when performing a transaction. When someone performs a transaction from a wallet, that wallet’s public key will be recorded on the blockchain and a Quantum adversary could easily calculate the corresponding private key to steal from that wallet. Dormant wallets with no public key exposed (only the hash address is visible) are much more difficult to drain funds from because recovering a public key from a hash is substantially more difficult than when the public key has been published.
2) Signature methods will be a more long-term issue. Bitcoin and Ethereum currently use ECDSA/Schnorr as their signature methods, both of which are susceptible to Shor’s Algorithm and will take many years of coordination, agreement on protocol updates, and the agreement of the networks to effect change.
Multiple studies, exemplified by CoinShares (2026), estimate that approximately 8% (or 1.7 million units of BTC in traditional P2PK addresses) of all current BTC holdings will be impacted by a real risk of Quantum Computing and that Quantum Computers (QC's) will not cause significant market impact on BTC. Asserting that between 25% and 50% of BTC holdings are vulnerable to Quantum Computer technology is greatly exaggerated.
In 2024, NIST completed the development of four key post-quantum standards (FIPS 203-205 for ML-KEM/ML-DSA/SLH-DSA), with an additional HQC encryption standard added in 2025 as a fall-back; these standards are designed to resist attacks from both Shor’s Algorithm and Grover’s Algorithm. As such, it is imperative that blockchain developers immediately begin planning for the transition to post-quantum cryptography as outlined in the NIST’s IR 8547.
The unique characteristics of blockchains present additional challenges; namely, they must gain consensus from a large number of people on a decentralized mechanism for upgrading. Despite this, some blockchain networks (e.g., Ethereum) have begun to pursue quantum-resistant solutions and outline them in their roadmap, while other networks (e.g., Bitcoin) have chosen a more cautious approach, resulting in slower implementation timelines.
Several projects currently exist to explore the use of hybrid signatures and migration paths to quantum-resistant digital signatures; however, the timeline for complete implementation could potentially range from 7 to 15 years (depending on the Q-Day timeline in question). As a result, there is currently no need for panic about the implementation of post-quantum methods; however, complacency should equally be avoided.
Quantum computing is not an immediate threat to Bitcoin or other cryptocurrencies. However, the threat is clearly defined, and will disrupt specific cryptographic primitives in the future, most notably signatures through Shor's Algorithm. There are already standards and research underway to prepare for quantum threats, and the tools to do so exist in the industry. However, all decentralized networks will need to work together to ensure their upgrades happen at the same time.
As for end users: Keep funds in new addresses, don't reuse cryptographic keys, and monitor developments in the protocols you use. The window of time available for preparation is present; how effectively each network uses it will ultimately determine the outcome.
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